Method of mounting and maintaining electric conductor in a drill string

ABSTRACT

An insulated electric conductor employed in a tubular drill string to transmit electric energy between subsurface and surface locations is arranged within the drill string in a wound, helical, coiled, looped, folded, overlapped or other convoluted configuration. Preferably, the convoluted conductor, or a portion thereof, is maintained in tension. The convoluted configuration provides an excess length of conductor stored within the drill string which enables the conductor to be extended as the drill string is lengthened.

libfz'b'b United States Patent 11 1.

Heilhecker et al. July 23 1974 [5 METHOD OF MOUNTING AND 2,196,3144/1940 Lee.. 324/8 MAINTAINING ELECTRIC CONDUCTOR IN glartm smun A DRILLSTRING 2,748,358 5/1956 Johnston 339/16 [75] Inventors: Joe K.Heilhecker; Donald B. Wood; 3,007,534 11/1961 Salnikov et al. ,175/104Karl 0 Heintz all of H uston; Tex 3,253,245 5/1966 Brandt 2 3,285,62911/1966 -Cullen et a1. 175/104 Asslgneei Esso Production Research p y,3,372,762 3/1968 Cullen et al. 175/104 Houston, Tex. [22] Filed: Apr,12, 1973 Primary Examiner-David H. Brown A rt L. h 1 pp No: 350,459t/omey Agent or Firm Robe Gra am [63] Continuation-impart of Ser. No.267,729, June 29,

1972, abandoned An insulated electrlc conductor employed 1n a tubulardrill string to transmit electric energy between subsur- [52] "5/57,,17'5/40 175/1O4, face and surface locations is arranged within the drill166/65 166/315 string in a wound, helical, coiled, looped, folded, over-511 1m. (:1 E21b 7/00, E2lb 47/12 lapped or Other-convolutedconfiguration- Preferably, [58 Field of Search 339/16; 174/47; 166/3 15,the convoluted conductor, or a portion fiis 166/65,, 65 M; 175 40 50 v104 57 maintained in tension. The convoluted configuration provides anexcess length of conductor stored within 5 References Cited the drillstring which enables the conductor to be ex- UNITED-STATES PATENTStended as the drill string is lengthened. 2,096,279 10/1937 Karcher339/16 x 25 Claims, 9 Drawing Figures PMENTED 2 3 I974 SHEEI 1 BF 3 FIG.2

METHOD OF MOUNTINGAND MAINTAINING ELECTRIC CONDUCTOR'IN'A DRILL STRINGCROSS REFERENCE TO RELATED APPLICATIONS This application is acontinuation-in-part of application Ser. No. 267,729, now abandonedfiled in the US.

Pat. Office on .Iune 29, 1972.

BACKGROUND OF INVENTION 1. Fieldof the Invention This invention relatesto an improved method for establishing and maintaining electriccontinuity through a drill string using an insulated-electric conductor.The invention can be employed in wellbore telemetry operations and otheroperations whereinit is desired to transmit electric energy between thesurface and a subsurface location in a well.

2. Description of the Prior Art In the drilling of oil wells, gas wells,and similar boreholes, it frequently is desirable to transmit electricenergy between subsurface and surface locations. One application whereelectrical transmission has received considerable attention in recentyears is found in wellbore telemetry systems designed to sense,transmit, and receive information indicative of a subsurface condition.This operation has become known in the art as logging while drilling? Amajor problem associated with -wellbore telemetry" systems proposed inthe past has been that of providing reliable means for transmitting anelectric signal between the subsurface and surface locations. Thisproblem can best be-appreciated by considering the manner in whichrotary drilling opera? tions are normally performed. In rotary drilling,a borehole is advanced by rotating a drill string provided with a bit.Lengths of drill pipe, usually about 30 feet long, are individuallyadded to the drill string as the borehole is advanced. In adapting anelectrical telemetry system to rotary drilling equipment, it will thusbe appreciated that the means for transmitting an electric signalbetween subsurface and surface locations must be such as to permit theconnection of additional pipe lengths to the drill string. An earlyapproach to the problem involved the use of a continuous electricalcable which was adapted to be lowered insidethe drill string and to makecontact with a subsurface terminal. This tech-' nique, however, requiredwithdrawing the cable each time an additional length was connected tothe drill string. A more recent approach involves the use of specialdrill pipe equipped with an electric conductor. Each pipe section isprovided with connectors that mate with connectors of an adjacent pipesection and thereby provide an electrical circuit across the joint (SeeUS. Pat. Nos. 3,518,608 and 3,518,609). Disadvantages of this'systeminclude the high cost of special pipe'sections, the use of a largenumber of electric connectors (one at each joint), and the difficulty ofmaintaining insulation of the electric connectors at each oint.

Although the advantages and desirability of telemetering informationfrom a subsurface location to the surface as drilling operationsprogress have long been appreciated, electrical telemetry systems havenot proven successful mainly because of the unavailability of a reliableand practical conductor for transmitting electric signals to thesurface.

SUMMARY OF THE INVENTION The method of the present invention is adaptedfor use in a well drilling operation wherein an insulated electricconductor disposed in a pipe string used to drill a well is employed totransmit electric energy between a subsurface location within the pipestring and the surface.

A novel feature of the invention resides in placing the electricconductor in the pipe string in a configuration such that the length ofthe conductor is substantially longer than the distance between thesubsurface and surface locations. This configuration provides an excesslength of conductor stored within the drill string. As each additionallength of pipe is connected into the pipe string, thereby increasing thedistance between the subsurface and surface locations, the conductor canbe extended through the additional length of pipe by withdrawing aportion of the excess length of conductor from within the pipe stringand threading it through the additional length of pipe.

Althoughthe conductor can be arranged within the pipe string in avarietyfof convoluted configurations to provide the excess length, thepreferred configuration is such that the conductor has overlappedlongitudinal portions which preferably ar'edisposed in parallel relationand extend axially with respect to the pipe string.

Another novel aspect of the present invention involves a method oflengthening a pipe string and electric conductor within the pipe stringas drilling pro- The method of the present invention permits the use ofa continuous conductor from the subsurface location substantially to thesurface. In the preferred embodi ment, only one connector, located nearthe surface, is exposed to the drilling fluid. Moreover, the method canbe employed in rotary drilling operations using conventional drill pipe.I

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view of welldrilling equipment provided with an electric conductor arranged withinthe pipe string in a preferred configuration.

FIG. 2 is a fragmentary view of FIG. 1 illustrating the disposition ofthe electric conductor at a time subsequent to that illustrated in FIG.1.

FIGS. 3-6 are schematic views illustrating a preferred sequence of stepsfor adding a length of pipe into the pipe string.

FIG. 7 is an enlarged fragmentary view, shown partially in longitudinalsection, of an improved apparatus useful in the present invention.

FIG. 8 is a top plan view of the upper guide of the assembly illustratedin FIG. 7.

FIG. 9 is a top plan view of the lower guide of the assembly illustratedin FIG. 7.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Conventional rotary drillingequipment, as schematically illustrated in F IG. 1, includes swivel l0,kelly 11, Y tubular drill string 12, and bit 13. These components,

.of pipe '12 between the bit 13 and the kelly 11, and the term pipestring refers to the complete column of pipe including' kelly l1..Themajor portion of the drill string 12 normally is composed of drill pipewith a lower portion being composed of drill collars. The drill string12 consists of individual pipe sections connected together in end-to-endrelation. In the lower three sections of FIG. 1, the diameters of theborehole and the drill string 12 have been expanded in relation to theupper section to reveal further details.

The borehole 17 is advanced by rotating thedrill string 12 and bit 13while at the same time drilling fluid is pumped through the drill string12 and up the bore hole annulus. The drilling fluid is delivered toswivel through a hose attached to connection 18 and is returned to thesurface fluid system through pipe 19. A

.kelly bushing 20 couples the rotary table 16 to the kelly 11 andprovides means fortransmittingpower from the rotary table 16 to thedrill string 12 and bit- 13. (The use of a power swivel eliminates theneed for the kelly and rotary table. The present-invention can be usedwith either system; for purposes of illustration, however, the inventionwill be described with reference to the kelly and rotary table system.)

As mentioned previously, it frequently is desirable to monitor asubsurface drilling condition during drilling operations. This requiresmeasuring a physical condition at the subsurface location, transmittingthis data as an electrical signal to the surface, and reducing thesignal to useful form. Typical situations where telemetry is applicablein drilling operations include drilling through abnormal pressure zones,drilling through zones where hole deviation is likely to be a problem,directional drilling, exploratory drilling, and the like.

Although the present invention may be employed in most any drillingoperation wherein an electric conductor isused in pipe string totransmit electric energy between a subsurface location and a surfacelocation, it finds particularly advantageous application in a wellboretelemetry system such as that illustrated in FIG. 1 comprising aninstrument 21, an insulated electric conductor 22, and receiver 23.

The instrument 21 capable of measuring a subsurface condition andgenerating an electric signal indicative or I representative of thatcondition is provided within the drill string 12. A variety of devicescapable of sensing a physical condition are available. These includetransducers for measuring pressure, temperature, strain and the like;surveying instruments for measuring hole deviation; and logginginstruments for measuring resistivity or other properties of subsurfaceformations. The instrument 21 may be powered by batteries or by energytransmitted through conductor 22. Alternatively, a subsurface generatordriven by fluid flowing through the drill string 12 may be used to powerinstrument 21.

The method of the present invention relates primarily to the electricconductor 22employed within the drill string to transmit electric energybetween surface and subsurface locations. The energy may be a signalgenerated by the subsurface instrument 21 and transmitted to thereceiver 23 at the surface. Alternatively, the energy may be electricpower transmitted from the surface to actuate or drive a subsurfaceinstrument or motor. Or, energy may be transmitted down the conductor 22to power the instrument 21, and simultaneously intelligence may betransmitted up the same conductor.

As applied in telemetry operations, it is, preferred that the energybeing transmitted be in the form of a pulsating signal. Information'canbe transmitted by varying-the number, amplitude, width or'spacing of atrain of electrical pulses, or it can be transmitted by modulating thefrequency or amplitude of the pulsating signal. More than one transduceror other device may be employedin the instrument 21 if desired, in whichcase a multiplexer may be used for sending the various signals over asingle conductor. r

The instrument2l may be mounted directly in the drill string 12 or,'asillustrated in FIG. 1, it may be a separate tool that is lowered intothe drill string 12 on the conductor 22.

The conductor 22 extends froma terminal on the subsurface instrument 21substantially through the drill string 12, and connects to a suitablesurface terminal which is electrically connected to receiver 23.'-Inthis preferred embodiment the conductor extends through the kelly andconnects; to a terminal at device 25 located at the upper end of thekelly 11. Kelly conductor 24 serves to interconnect conductor 22 anddevice 25. It should be observed, however, that conductor 24 may beembedded in the kelly 11, in which case the conductor 22 will extend tothe upper end of the drill string 12 and connect to conductor 24 at thatlocation. In order to facilitate the addition of pipe sections to thedrill string 12, however, it is preferred that conductor 24 be disposedwithin kelly 11 as illustrated and extend slightly more than the lengthof one pipe section below the kelly 11.

If telemetry operations are to be performed while the kelly 11 and drillstring 12 are rotating, the upper end of conductor 24 will be connectedto device 25 capable of transmitting electric energy from a rotatingmember to a stationary member. Device 25 may be a rotary transformerhaving a rotor secured to the kelly 11 and a stator secured to thestationary portion of the swivel 10, or it may be a slip ring and brushassembly. Device 25 and electric conductor 38 provides means fortransmitting signals from the conductor within the pipe string toreceiver 23. The return path for the electric circuit may be provided bya variety of grounding circuits but preferably is through the'pipestring or conductor armor. Conductor 39 of the return path interconnectsstationary portion of device 35 and receiver 23. If telemetry operationsare to be performed at times when the drill string 12 and kelly 11 arestationary, the conductors 38 and 39 may be connected directly toconductor 24 through a suitable connector. In this situation, conductors38 and 39 will be disconnected when the kelly 11 and drill string 12 arerotated. Other means for transmitting the signal to the receiver 23include a wireless transmitter connected to conductor 22 and located ona rotating member, e.g. kelly 11.

The receiver 23 is an instrument capable of receiving the signalgenerated by instrument 21 and reducing it to useful form. Y

In accordance with one aspect of the present invention, the conductor 22is arranged within the drill string 12 in a configuration such that thelength of the conductor22 is substantially longer than the distancebetween the subsurface location of instrument 21 and a surface location.As described in detail below, the excess length of conductor 22 storedin the drill string 12 permits the conductorv 22 to be extended as thedrill string 12 is lengthened. A portion of the conductor 22 is arrangedin a wound, coiled, helical, folded, looped or other convolutedconfiguration that provides the excess length. It is preferred, however,that the conductor 22 be arranged in an overlapped configuration .suchas that illustrated in FIGS. 1 and 7. This configuration provides theconductor 22 with longitudinal portions 26, 27, and 28 which aredisposed in parallel relation and extend axially with respect to thedrill string 12. Theoverlapped configuration permits the excess lengthof conductor to be almost double the distance between the subsurfacelocation of the instrument 21 and the surface.

The apparatus for installing and maintaining the conductor 22 in theoverlapped configuration comprises an upper guide 29 secured to thedrill string 12, and a lower movable guide 30. In the installedposition, the conductor 22 extends upwardly from the instrument 21-,around the upper guide 29, downwardly from the upper guide 29, aroundthe lower guide 30 and upwardly from the lower guide 30 to the upper endof the drill string where it connects to conductor 24. The guides 29 and30 are shown schematically in FIG. 1 and in detail in FIGS. 7-9.

As best seen in FIG. 4, conductor 24 has a lower tail section 33 whichextends slightly more than the length of one pipe section below kelly11. The lower end of tail section 33 is provided with connector 32 whichis adapted to mate with connector 31 attached to the upper end ofconductor 22. The conductor 22 is thus joined to conductor 24 at a pointslightly below the top pipe section 34 of the drill string 12 (see FIG.3). The electric conductor thusextends from a terminal on. instrument 21to a surface terminal within kelly 11 and comprises conductor 22 andconductor 24 connected together by connectors 31 and 32.

The connectors 31 and 32, in addition to providing a water tightconnection, should have sufficient mechanical strength to support theconductor 22 and associated subsurface equipment. For example, thisconnection may be provided by a threaded housing or it may be providedby an assembly which includes latching dogs to impart sufficientmechanical strength to the connectors.

As mentioned previously, the excess conductor, e.g. overlapped portions27 and 28,- permitthe conductor 22 to be extended as the drill string 12is lengthened. The drill string 12 is normally composed of individualpipe sections approximately 30 feet in length. A length of pipe will beadded to the drill string l2for each incremental advance of the borehole17. Normally the additional length of pipe is one pipe section-However,the additional length may include two or more pipe sections connectedtogether. In any event, the borehole advancement is sufficient to permitthe addition of a length of pipe. Each additional length of pipe, onepipe section in this example, may be connected into the pipe string bythe procedure described below with reference to FIGS. 3 and 6. Theprocedure for installing the equipment as depicted in FIG. 3 will bedescribed later.

As shown in FIG. 3 drilling has progressed to the point that oneadditional pipe section, e.g. section 36, must be added into the pipestring 12. Pipe section 36 is disposed in a shallow borehole 37(commonly referred to as a mouse hole) below the derrick fioor.Initially, the kelly 11 and drill string 12 are elevated and the drillstring 12 is suspended in the rotary table 16. The kelly 11 is thendisconnected from the drill string 12 and is elevated sufficiently topull the tail section 33 of kelly conductor 24 completely out of thedrill string 12. Thus the kelly 11 is elevated slightly more than thelength of one pipe section. As the kelly 11 is elevated, the matedconnectors 31 and 32'and a portion of conductor 22 are pulled throughthe top pipe section 34 of the drill string 12. This also pulls thelower guide 30 up the drill string 12 a distance about equal to one-halfthe length of pipe section 34 and shortens theoverlapped portions 27 and28 of conduc tor 22. With a slotted support plate 35 positioned betweenconnector 31' and pipe section 34 to support the upper end of conductor22, connector 32 is separated from connector 31 breaking electriccontinuity and placing the equipment in the condition illustrated inFIG.4.

. The kelly 11 is then swung over into alignment with the pipe section.36. The tail section 33 of conductor 24 is threaded through the pipesection 36 and the kelly 11 is joined to the upper end of pipe section 36 (see FIG. 5). The kelly 11 and pipe section 36 are then raised andaligned with the drill string 12. The tail portion 33 extends a shortdistance, e.g. 1-3 feet, below pipe section 36 permitting the connector32 to be mated with connector 31 reestablishing electric continuity fromthe subsurface terminal at instrument 21 to the surface terminal atdevice 25. With the connectors 31 and 32 mated, the support plate 35 isremoved. The lower guide 30 draws the connectors 31 and 32 a shortdistance downwardly into the drill string 12. If internal upset drillpipe is used, the tail portion 33 preferably should be sufficiently longto permit the connectors 31 and 32 to move downwardly within the drillstring 12 to clear the upset restriction at the pipe joint.

The lower end of pipe section 36 is then connected to the drill string12 (see FIG. 6). Section 36 thus is inserted or added into the pipestring by connecting one end to the drill string 12 and the other end tokelly 11. The kelly 11 and drill string 12 are then lowered until thekelly bushing 20 engages the rotary table 16. Drilling will thencontinue until another pipe section must be added. The upper end ofconductor 22 is threaded upwardly through the additional pipe section36, and another pipe section is added into the pipe string by theprocedure described above and depicted in FIGS. 3-6. This operation maycontinue until the excess length of conductor 22 is used up. This occurswhen the lower guide 30 engages or approaches upper guide 29 (see FIG.2). The conductor 22, guides 29 and 3t) and instrument 21 are thenwithdrawn from the drill string 12. It should be observed, however, thatthe excess length of conductor can be restored within the drill string12 after it has been completely or partially used up. This may beachieved by merely connecting a conductor of the desired length'to theupper terminal end 31 of conductor 22 and introducing an additionallength of conductor into the drill string 12. The lower guide 30 is thuslowered within the drill string 12, increasing the lengths of overlappedportions 27 and 28.

The amount of conductor that can be added in this provided with a groove62, the radius of which is approximately equal to the radius ofconductor 22.

Each of the arms 43 fits into a longitudinal slot 46 formed in the body41 and is pivotable about a pin 47. The length of each slot 46 is such.that an arm 43 mounted therein can be pivoted about pin 47 to a fullyretracted position within slot 46. An upper,- flat surface 49 of eacharm 43 engages a downwardly facing surface formed in body 41. The arms43 extend radially outwardly beyond the internal diameter of the drillstring 12 and are adapted to rest on an annular notched shoulder 50formed in the box end of a pipe section.

Shoulder '50 may be provided by milling the box end of the pipe sectionin which guide 29 is to be retained, or alternatively may be provided bya special sub. Each arm may also be secured to body 46 by a shear pin 48to prevent the upper guide 29 from being jarred out of the mountingnotch.

The lower guide 30 includes a body 51, a sheave 52, and a weight 53. Thebody 51 has an upper nose section 54 provided with a side opening slot55. The width of slot 55 is slightly larger than the diameter ofconductor 22. The sheave 52 is journalled in body 51 by bolt 57 andbearing 58. The weight 53 attached to the lower end of body 51 maybeprovided by a plurality of cylindrical sections connected together inend-to-end relation and may include a centralizer 60 secured thereto.The weight 53 should be sufficiently large to maintain a downwardbiasing force on the conductor to remove or reduce slack in at least aportion of the conductor. Preferably, the weight should maintain theconductor in tension. Experience has shown that slack cable can bedamaged by drilling fluid flowing through the drill string 12. A40-pound'weight has served satisfactorily for a three-sixteenth incharmored cable.

The surface equipment for lowering or raising the conductor 22 andassociated equipment within the drill string 12 can be similar tocablehandling equipment used in well logging operations. Such equipmentnormally includes a power winch containing a conductor wound thereon anda sheave suspended from the rig drawworks for guiding the conductor intoor out of the drill string 12.

' The conductor 22 andassociated equipment may be installed in the drillstring 12 by the following procedure. With the kelly 11 disconnectedfrom the drill string 12, instrument 21 is lowered into the drill string12 on conductor 22. The conductor 22 is unreeled from a power winch andfed into the drill string 12 until the instrument 21 reaches the desiredsubsurface location. The drill string 12 normally will be provided with8 a suitable releasable latching means for receiving and engaging theinstrument 21.

With the instrument 21 properly located, the conductor 22 extends to thesurface. On the rig floor, the conductor 22 is wound about the upper andlower guides 29 and 30 in the configuration shown in FIG. 7, except thatthe guides 29 and 30 will be positioned in end-toend abuttingengagement. In installing the conductor 22 on guide 30, the sheave 52 isfirst removed from body 51 by disconnecting'bolt 57, and with theconductor 22 wound thereon is reinstalled on body 51. The guides 29 and30 with conductor wound thereon is then inserted into the upper end ofthe drill string 12. Arms 43 of the upper guide 29 fit into the notchesof shoulder 50.

At this point, it will be observed that the conductor. 22 extends frominstrument 21 upwardly to the upper guide 29, around semiconductormember 42, downwardly to the lower guide 30, around sheave 52, andupwardly through slot of guide 30 and opening 44 of guide 29. Thisarrangement provides the conductor 22 witha convoluted configurationcomprising overlapped portions 26, 27, and 28. The lower guide 30 issuspended on a loopedportion of the conductor 22. Additional length ofconductor 22 is then unreeled from the winch and fed through opening 44of the upper guide 29 lowering the lower guide 30 in the drill string12. Overlapped portions 27 and 28 are lengthened as the lower guide 30descends within the drill string 12. The conductor 22 which extends fromthe instrument 21 to the upper guide 29 passes between adjacent bowsprings of centralizer (if used) and through a guide member 61 strappedto the weight 53. Member 61 and centralizer 60 prevent the lower guide30 from twisting with respect to the upper guide 29.

The conductor 22 is fed into the drill string 12 until its upperterminal end provided with connector 31 engages the upper guide 29. Inthe embodiment wherein the kelly 11 is provided with conductor 24 asillustrated in FIG. 4, it is preferred to position connector 31 a shortdistance above the upper guide 29. This may be achieved by adding a pipesection, preferably a short pipe section, to the drill string 12 andpulling the connector 31 and a portion of conductor 22 through the shortpipe section. A second pipe section is then added to the drill string 12in the manner described above with reference to FIGS. 3-6. The shortpipe section permits the mated connectors 31 and 32 to be lowered ashort distance below the top pipe section'of the drill string withoutengaging guide 29 and the second pipe section is needed to accommodatethe tail section 33 of conductor 24.

In other embodiments, as for example where conductor 22 connects to aconductor embedded in kelly 11 and no tail section is employed, it willnot be necessary to use the short pipe section or to add the second pipesection.

During drilling operations, additional pipe sections are added to thedrill string 12 as the borehole 17 is advanced until it becomesnecessary to change the drill bit 13 or until the excess length ofconductor 22 is used up. Thelength of excess conductor 22 stored in thedrill string normally will be sufficient to complete at least one bitrun. The capabilities of a particular bit, of course, will depend on thetypes of strata being drilled but normally will be between about 500 and3,0110 feet.

'30 abuts the upper guide 29. A sufficient amount of v borehole may bereinstalled in the drill string 12. How- When it becomes necessary towithdraw the drill Weigh string 12 from the borehole, as for example toreplace .Mmeflal Brass the bit 13,'the conductor 22 and associatedequipment b efi p h pi will first be retrieved from the drill string 12by the fol- 1jf,,,i,;-"" es 2 4Q. lowing procedure. The kelly 11 isdisconnected from the drill string 12 and the mated connectors 31 and 32are pulled through the top pipe section of the drill string 12.Connector 32 is disconnected from connecf Th d ill i h d an t id di m f4 5 o and conductor 22 is Withdrawn r drill inches, an inside diameterof 3.64 inches, and an upset string 12 by reeling it on a power winch.The excess inside diameter of 2.81 inches. The upper and lower portions27 and 28 are shortened until the lower guide id assembly with the cableproperly arranged I thereon was then placed in the upper end of thedrill tension 15 then pulled on the conductor 22 to shear the i Ab t 600f t f c bl were i t d d i t th shear P 48 used) holding the arms 0f h ppr drill pipe forming overlapped portions having lengths guide 29iflplace- This Permits the arms to Pivot free I 15 'of about 300 feeteach. This arrangement provided of shoulder 50 and toretractwithin body41 which reb t 1,000 f t f bl di d i the d ill i 163565 the pp guide 29from the drill String The about 600 feet of which was excess'cable.Drilling mud assembly is then retrieved from the drill string 12. Thewas flowed through the drill pipe for about 2 hours. apparatus isdisconnected from the conductor 22 and Th bl and g id w th n withd f oth the remaining conductor 22 with the instrument 21 is ldrill pipewithout difficulty. g retrieved. The drill string 12 is then; withdrawnin the A variation of the invention involves use of a separate usualmanner. The drill string 12 with a new bit 13 is retriever cable forpulling the conductor 22 through a lowered into the borehole. With thebit 13 located 1 length of pipe to be added to the drillstring; In'thisvariabout two pipe lengths above the bottom of the borev Zation, theretriever cable which can bela 'wireline is hole, the conductor 22 whichwas withdrawn from the 25 threaded through the length of pipe to beadded to the drill string. With the additional length of pipe suspendedin elevators above the drill string, the retriever a longer conductormust be employed. I Icable is connected to the upper terminal end ofcon- The conductor '22 usable in the preferred embodiductor; one end ofthe additional pipe length is conment of the present invention shouldhave the following necteclto the drill string; the retriever cable ispulled properties. it should have a breaking strength suffi- Lthroughthe additional pipe length threading conductor cientlyhigh to supportthe guides 29 and 30 and instru- 22 upwardly through the additional pipelength. The ment 21 and to permit shearing'of pins 48 (if used); itconductor 22 is reconnected to conductor 24' and should have anoperating temperature at least equal to added pipe is connected .tokelly 11. In this embodi the maximum subsurface temperature encountered;ment it should be noted that the threading or extending and it should besufficiently flexible to permit it to be ,of a portion of conductor 22is performed before the arranged'in the proper convoluted configuration.One particular conductor that has been successfully tested is a ngleconductor three-sixteenth inch armored cable manufactured by VectorCable Company and sold as type 1-18P. Tests have shown that this cablecan be bent around guides having a 2-inch pitch diameter. The testsemployed upper and lower guides similar to those illustrated in FIGS. 7,8, and 9. Materials and dimensions of the upper and lower guides were asfol- An instrument suspended on the cable was lowered into internalupset drill pipe to a depth of about 400 ever, if additional excesslength of conductor is desired,

string; in the embodiment described earlier, the step of extending theconductor was performed after the additional length of pipe wasconnected into the pipe string.

As mentioned previously, the present invention also contemplates animproved method for lengthening a pipe string while at the-same timelengthening an electric conductor provided therein. The method involveslowering an insulated conductor 22, preferably an arlows: mored cablefree of connectors, to a subsurface terminal near the lower end of apipe string used to drill a U H Guide 29 I well; threading a conductorsection, e.g., section 33, R do Tai 50 through a length of pipe to beadded to the pipe string;

connecting the conductor section 33 to conductor 22;

, Material AlSl l0l8 Steel 1 outside diameter inches 13/18 and finallyconnecting the pipe length into the pipe semicircuar Length. inchest.4"/nr i string. The conductor section 33 preferably is con- Member(42) i nected to a surface terminal; it may also be initially disy M I Sconnected from the surface terminal and connected to i ffl Q 1018. teethe surface terminal during the operation for lengthenlitch diameter,inches 2 ing the pipe string and conductor.

Arms (43) Although the present invention has been described Materialpast 1018 Steel with reference to conventional rotary drilling opera- 1i I tions, it can also be used with other types of drilling ends. inches1 Lower Guide 30): equipment including turbo drills and positivedisplace- Y ment hydraulic motors. These devices normally include MmmalEms a motor or turbine mounted on the lower end of the gg f n h ,drillstring and adapted to connect to and drive a bit. sheave (52) e es 5 Themotor or turbine powered by the drilling fluid drives the drill bitwhile the drill string remains stationmfggafl inches g' BT91? ary. Whenthis type subsurface drilling device is used W dth... indies.

additional lengthof pipe is connected into the pipe provides a highlyuseful means for transmitting direcsaid drill string and a locationsubstantially at the surface, the improvement which comprises placingsaid conductorin said drill string in a configuration such that thetotal length of said conductor is substantially.

longer than the distance between said subsurface and surface locations;adding a length of pipe to said drill string to increase the distancebetween said subsurface and surface locations; and threading saidconductor' through said length of pipe.

2. In a well, drilling operation wherein an insulated electric conductoris employed internally of a pipe stringto transmit electric energybetween a subsurface location and a location substantially at thesurface, an improved method for extending said electric conductorthrough lengths of pipe which are individually added to said pipestringas the drilling progresses which comprises storing alength ofconductor within said pipe string which is in excess of the distancebetween said locations; extending a portion of said electric conductorthrough a length, of pipe to be added into said pipe string; connectingsaid length of pipe into said pipe string. 3. A method as defined inclaim 2 wherein the step of storing a length of conductor in the pipestring provides an. excess length of conductor atleast equal to saidlength of pipe to be added into said pipe string.

4. A method of installing an insulated electric conductor in a tubulardrill string in a well which comprises placing said conductor internallyof said drill string; ar-

apart to remove slack in said conductor.

6. In a method of drilling a well wherein an insulated electricconductor is employed in a pipe-string to transmit electric energybetween subsurface and surface 10- cations in said pipe string, theimprovement which comprises placing said conductor in said pipe stringin a configuration such that the length of said conductor issubstantially longer than the distance between said subsurface andsurface locations; and extending said conductor through individuallengths of pipe as each of saidlengths is added to said pipe string.

7. A method as defined in claim 6 wherein the step of extending saidconductor through individual lengths of pipe is performed after each ofsaid lengths of pipe is added into said pipe string.

8. A method as defined in claim 6 wherein the step of extending saidconductor through individual lengths 1 of pipe is performed before each,of said lengths of pipe is added to said pipe string.

9. A method as defined in claim 6 wherein the configuration of saidconductor'is convoluted.

10. A method asdefined in claim 6 wherein the step of extendingsaidconductor includes withdrawing a portion of said conductor from saidpipe string and threading said portion through each length of pipe assaidjength of pipe is added tosaid pipe string.

11. A method as defined in claim 6 wherein said conductor is placed insaid pipe string in a configuration such as to provide overlappedportions having an upper loop and a lower loop.

12. A method as defined in claim 11 wherein the lower loop is biaseddownwardly to remove slack from a portion at least of said conductor.

13. A method of establishing and maintaining electric continuity betweena subsurface location and surface locationin a pipe string used to drilla well which comprises placing an electric conductor in said pipe stringwhich extends between said subsurface and surface '10- cations and whichhas a length substantially in excess of the distance between saidsubsurface and surface locations; advancing said well sufficiently torequire lengthening said pipe string; adding a length of pipe into saidpipe string; and extending a portion of said electric conductor throughsaid length of pipe.

14. A method of establishing electric continuity within a pipe string ina well'between a subsurface location and a location substantially at thesurface which comprises placing an insulated electric conductor in saidpipe string to extend from said subsurface location to said surfacelocation; convoluting atleast a portion of said conductor withinsaidpipe string such that the length of said conductor in said pipestring exceeds the distance between said subsurface and surfacelocations; and tensioning at least a portion of said conductor to reduceslack in said conductor.

15. In a method of drilling a well using a pipe string wherein the pipestring is lengthened as the-well becomes deeper 'by disconnecting thepipe string at the surface and adding a length of pipe into the pipestring by connecting said length of pipe at each end to the pipe string,the method of providing electric continuity 4 between a subsurfacelocation in the pipe string and a location substantially at the surfaceof the well, which comprises placing an insulated'electric conductor inthe well within the pipev string to extend from said subsurface locationnear the lower end of said pipe string to said surface location, saidconductor having a length substantially in excess of the distancebetween said subsurface and surface locations; breaking said electriccontinuity by separating said conductor substantially at the surfacewhenthe addition of said length of pipe is to be made into the pipe string;and reconnecting'said electric conductor before both ends of theadditional length of pipe are connected into said pipe string to includea length of electric conductor extending through 50 said additionallength of pipe.

16. A method as defined in claim 15 which includes the step-of removingslack from at least a portion of the conductor in the pipe string.

17. A method as defined in claim 15 in which a por- 55 tion of theconductor in the pipe string is withdrawn therefrom after the conductoris separated and is extended through said additional length of pipe.

18. A method as defined in claim 15 in which at least a portion of theelectric conductor lowered within the pipe string is convoluted suchthat the length of said e 1 w q a.

i 13 upper loop is supported on said pipe string and said lower loop isbiased downwardly.

22. In a method of drilling a well using a pipe string, an improvedmethod of establishing and maintaining electric continuity through saidpipe string between a subsurface location in the well-and a surfacelocation which comprises lowering in said pipe string an insulatedelectric conductor to extend between said locations and having asubstantially length in excess of the distance between said locations;advancing said well sufficiently to require the insertion of anadditional length of pipe into said pipe string; disconnecting said pipestring and separating said electric conductor at the surface; threadingelectric conductor through an additional length of pipe; reconnectingsaid electric coni ductor to reestablish electric continuity betweensaid locations through said pipe string including said additional lengthof pipe; and inserting said additional length of pipe into said pipestring.

23. A method of establishing and maintaining electric continuity in adrill string in a well as said well is being drilled which compriseslowering an insulated electric conductor in said drill string to extendfrom a subsurface location near the lower end of said drill stringsubstantially to the surface; convoluting a portion of said conductorsuch that the length of conductor in said drill string is in excess ofthe distance between said subsurface location and the surface; threadingan electric conductor section through a length of pipe to be added tosaid drill string; connecting said conductor section to said electricconductor; and connecting said length of P E9ld drill w s n 0 near thesurface; withdrawing a conductor section from said pipe string;separating said conductor section from 24. A method for establishing andmaintainingelec tric continuity between a subsurface terminal within apipe string used to drill a well and a surface terminal which comprisesplacing an insulated electric conductor in said pipe string to extendbetween said terminals and which has a length substantially in excess ofthe distance between said terminals; advancing said well sufficiently torequire an additional length of pipe in said pipe string; disconnectingsaid pipe string at a point the remainder of said conductor; threadingsaid conductor section through a length of pipe; reconnecting saidconductor section to the remainder of said conductor; and connectingsaid length of pipe into said pipe string.

25. A method of electrically connecting a first electric terminallocated within a pipe string at a subsurface location in a well with asecond electric terminal loelectric conductor.

1. In a method of drilling a well wherein an insulated electricconductor is employed in a drill string to transmit electric energybetween a subsurface location in said drill string and a locationsubstantially at the surface, the improvement which comprises placingsaid conductor in said drill string in a configuration such that thetotal length of said conductor is substantially longer than the distancebetween said subsurface and surface locations; adding a length of pipeto said drill string to increase the distance between said subsurfaceand surface locations; and threading said conductor through said lengthof pipe.
 2. In a well drilling operation whErein an insulated electricconductor is employed internally of a pipe string to transmit electricenergy between a subsurface location and a location substantially at thesurface, an improved method for extending said electric conductorthrough lengths of pipe which are individually added to said pipe stringas the drilling progresses which comprises storing a length of conductorwithin said pipe string which is in excess of the distance between saidlocations; extending a portion of said electric conductor through alength of pipe to be added into said pipe string; connecting said lengthof pipe into said pipe string.
 3. A method as defined in claim 2 whereinthe step of storing a length of conductor in the pipe string provides anexcess length of conductor at least equal to said length of pipe to beadded into said pipe string.
 4. A method of installing an insulatedelectric conductor in a tubular drill string in a well which comprisesplacing said conductor internally of said drill string; arranging saidconductor to form overlapped portions having an upper loop and a lowerloop within said drill string; and introducing additional conductor intosaid drill string while lowering said lower loop within said drillstring to lengthen the overlapped portions.
 5. A method as defined inclaim 4 and further comprising biasing said upper loop and said lowerloop apart to remove slack in said conductor.
 6. In a method of drillinga well wherein an insulated electric conductor is employed in a pipestring to transmit electric energy between subsurface and surfacelocations in said pipe string, the improvement which comprises placingsaid conductor in said pipe string in a configuration such that thelength of said conductor is substantially longer than the distancebetween said subsurface and surface locations; and extending saidconductor through individual lengths of pipe as each of said lengths isadded to said pipe string.
 7. A method as defined in claim 6 wherein thestep of extending said conductor through individual lengths of pipe isperformed after each of said lengths of pipe is added into said pipestring.
 8. A method as defined in claim 6 wherein the step of extendingsaid conductor through individual lengths of pipe is performed beforeeach of said lengths of pipe is added to said pipe string.
 9. A methodas defined in claim 6 wherein the configuration of said conductor isconvoluted.
 10. A method as defined in claim 6 wherein the step ofextending said conductor includes withdrawing a portion of saidconductor from said pipe string and threading said portion through eachlength of pipe as said length of pipe is added to said pipe string. 11.A method as defined in claim 6 wherein said conductor is placed in saidpipe string in a configuration such as to provide overlapped portionshaving an upper loop and a lower loop.
 12. A method as defined in claim11 wherein the lower loop is biased downwardly to remove slack from aportion at least of said conductor.
 13. A method of establishing andmaintaining electric continuity between a subsurface location andsurface location in a pipe string used to drill a well which comprisesplacing an electric conductor in said pipe string which extends betweensaid subsurface and surface locations and which has a lengthsubstantially in excess of the distance between said subsurface andsurface locations; advancing said well sufficiently to requirelengthening said pipe string; adding a length of pipe into said pipestring; and extending a portion of said electric conductor through saidlength of pipe.
 14. A method of establishing electric continuity withina pipe string in a well between a subsurface location and a locationsubstantially at the surface which comprises placing an insulatedelectric conductor in said pipe string to extend from said subsurfacelocation to said surface location; convoluting at least a portion ofsaid conductor within said pipe string such that the length of saidconductor in sAid pipe string exceeds the distance between saidsubsurface and surface locations; and tensioning at least a portion ofsaid conductor to reduce slack in said conductor.
 15. In a method ofdrilling a well using a pipe string wherein the pipe string islengthened as the well becomes deeper by disconnecting the pipe stringat the surface and adding a length of pipe into the pipe string byconnecting said length of pipe at each end to the pipe string, themethod of providing electric continuity between a subsurface location inthe pipe string and a location substantially at the surface of the well,which comprises placing an insulated electric conductor in the wellwithin the pipe string to extend from said subsurface location near thelower end of said pipe string to said surface location, said conductorhaving a length substantially in excess of the distance between saidsubsurface and surface locations; breaking said electric continuity byseparating said conductor substantially at the surface when the additionof said length of pipe is to be made into the pipe string; andreconnecting said electric conductor before both ends of the additionallength of pipe are connected into said pipe string to include a lengthof electric conductor extending through said additional length of pipe.16. A method as defined in claim 15 which includes the step of removingslack from at least a portion of the conductor in the pipe string.
 17. Amethod as defined in claim 15 in which a portion of the conductor in thepipe string is withdrawn therefrom after the conductor is separated andis extended through said additional length of pipe.
 18. A method asdefined in claim 15 in which at least a portion of the electricconductor lowered within the pipe string is convoluted such that thelength of said conductor between said subsurface and surface locationsexceeds the distance between said locations.
 19. A method as defined inclaim 18 wherein said convoluted conductor includes overlapped portionshaving an upper loop and a lower loop.
 20. A method as defined in claim19 and further comprising biasing said upper and lower loops apart. 21.A method as defined in claim 19 wherein said upper loop is supported onsaid pipe string and said lower loop is biased downwardly.
 22. In amethod of drilling a well using a pipe string, an improved method ofestablishing and maintaining electric continuity through said pipestring between a subsurface location in the well and a surface locationwhich comprises lowering in said pipe string an insulated electricconductor to extend between said locations and having a substantiallylength in excess of the distance between said locations; advancing saidwell sufficiently to require the insertion of an additional length ofpipe into said pipe string; disconnecting said pipe string andseparating said electric conductor at the surface; threading electricconductor through an additional length of pipe; reconnecting saidelectric conductor to reestablish electric continuity between saidlocations through said pipe string including said additional length ofpipe; and inserting said additional length of pipe into said pipestring.
 23. A method of establishing and maintaining electric continuityin a drill string in a well as said well is being drilled whichcomprises lowering an insulated electric conductor in said drill stringto extend from a subsurface location near the lower end of said drillstring substantially to the surface; convoluting a portion of saidconductor such that the length of conductor in said drill string is inexcess of the distance between said subsurface location and the surface;threading an electric conductor section through a length of pipe to beadded to said drill string; connecting said conductor section to saidelectric conductor; and connecting said length of pipe to said drillstring.
 24. A method for establishing and maintaining electriccontinuity between a subsurface terminal within a pipe string used todrill a well and a surface terminal which comprises placing an insulatedelectric conductor in said pipe string to extend between said terminalsand which has a length substantially in excess of the distance betweensaid terminals; advancing said well sufficiently to require anadditional length of pipe in said pipe string; disconnecting said pipestring at a point near the surface; withdrawing a conductor section fromsaid pipe string; separating said conductor section from the remainderof said conductor; threading said conductor section through a length ofpipe; reconnecting said conductor section to the remainder of saidconductor; and connecting said length of pipe into said pipe string. 25.A method of electrically connecting a first electric terminal locatedwithin a pipe string at a subsurface location in a well with a secondelectric terminal located near the surface of the well which compriseslowering within the pipe string an electric conductor which is longerthan the distance between the terminals; securing the lower end of saidconductor at said subsurface location in electrical connection with saidfirst electric terminal; locating the upper end of said conductor atsaid surface location in electrical connection with said second electricterminal; and convoluting and tensioning at least a portion of saidelectric conductor between said terminals so as to remove slack in saidelectric conductor.